Deviated drilling system utilizing steerable bias unit

ABSTRACT

A technique facilitates steering during, for example, a borehole drilling operation. The technique employs a drill string comprising a drill bit and a steering tool for controlling the trajectory of a borehole formed by rotating the drill bit. The steering tool includes a main body and a steering sleeve pivotably mounted to the main body by a joint located to enable pushing contact via the steering sleeve against a surrounding borehole wall at a location between the joint and the drill bit. The steering sleeve is selectively pivoted by a plurality of actuators disposed between the main body and the steering sleeve.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority to U.S. ProvisionalApplication Ser. No.: 62/128,451, filed Mar. 4, 2015, which isincorporated herein by reference in its entirety.

BACKGROUND

Drilling systems are employed for drilling a variety of wellbores. Adrilling system may comprise a drill string and a drill bit which isrotated to drill a wellbore through a desired subterranean formation. Invarious drilling applications, a desired borehole trajectory is plannedand calculated prior to drilling based on geological data. A number ofsteering techniques and equipment types may be employed to achieve aplanned trajectory. For example, a bottom hole assembly may comprise arotary steerable tool used to enable directional drilling while rotatingthe drill string. Rotary steerable drilling systems utilize variouscomponents including stabilizers, actuator pads, and other components tocontrol the drilling direction. However, existing systems tend to becomplex assemblies with multiple moving parts, and this complexity canlead to service quality issues and downtime. For example, existingpush-the-bit rotary steerable systems sometimes incur seal failure,cracking hinge bushes, hinge pin bending, and high wear rates onactuator pads. Existing systems also may have limitations in certainapplications due to external moving parts, actuator pads positioned asubstantial distance from the drill bit, and limited actuation force.

SUMMARY

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofthe claimed subject matter. In some embodiments, a system for use in awell includes a drill string including a drill bit and a steering toolfor controlling the trajectory of a borehole formed by rotating thedrill bit. The steering tool includes a main body and a steering sleevepivotably mounted to the main body by a joint located to enable pushingcontact via the steering sleeve against a surrounding borehole wall at alocation between the joint and the drill bit. The steering sleeve isselectively pivoted by a plurality of actuators between the main bodyand the steering sleeve.

In some embodiments, a method of drilling includes pivotably coupling asteering sleeve, having a sacrificial liner, to a main body to form asteering tool. The sacrificial liner positioned along an interior of thesteering sleeve is used. A plurality of actuators are located betweenthe main body and the steering sleeve. The steering tool is coupled to adrill bit. The method further includes rotating the drill bit andcontrolling the drilling orientation of the drill bit by selectivelyactuating selected actuators of the plurality of actuators to cause thesteering sleeve to pivot against a surrounding borehole wall, thuspushing the drill bit. In some embodiments, a system includes a steeringtool operable to control a trajectory of a borehole during drilling ofthe borehole. The steering tool includes a main body and a steeringsleeve pivotably mounted to the main body by a gimbal joint to enablepushing contact via the steering sleeve against a surrounding boreholewall. The steering sleeve is selectively pivoted by a plurality ofactuators disposed between the main body and the steering sleeve.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the disclosure will hereafter be described withreference to the accompanying drawings, wherein like reference numeralsdenote like elements. It should be understood, however, that theaccompanying figures illustrate the various implementations describedherein and are not meant to limit the scope of various technologiesdescribed herein, and:

FIG. 1 is a schematic illustration of an example of a drilling systemdeployed in a wellbore, according to an embodiment of the disclosure;

FIG. 2 is a cross-sectional illustration of an example of a steeringtool system which may be positioned in a drilling system, e.g. thedrilling system illustrated in FIG. 1, according to an embodiment of thedisclosure;

FIG. 3 is a cross-sectional illustration of an example of a gimbal jointwhich may be employed in the steering tool system, according to anembodiment of the disclosure;

FIG. 4 is an illustration of the gimbal joint shown in FIG. 3 butdemonstrating the multiple degrees of rotational freedom, according toan embodiment of the disclosure;

FIG. 5 is a cross-sectional illustration of an example of a steeringtool system which may be positioned in a drilling system, e.g. thedrilling system illustrated in FIG. 1, according to an embodiment of thedisclosure;

FIG. 6 is a cross-sectional view taken generally through line 6-6 ofFIG. 5, according to an embodiment of the disclosure; and

FIG. 7 is a side view of the embodiment of the steering tool systemillustrated in FIG. 5, according to an embodiment of the disclosure.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of some embodiments of the present disclosure. However,it will be understood by those of ordinary skill in the art that thesystem and/or methodology may be practiced without these details andthat numerous variations or modifications from the described embodimentsmay be possible.

The present disclosure generally relates to a system and methodologywhich facilitate steering during, for example, a borehole drillingoperation. For example, the technique facilitates directional drillingapplications by providing a steerable drilling system, e.g. a rotarysteerable drilling system, with improved performance, greaterdependability and lower cost. In an embodiment, the rotary steerabledrilling system is constructed with a relatively low number ofcomponents arranged to enable improved use of mechanical advantage andto produce higher steering forces while operating at a lower pressuredrop, thus reducing the risk of erosion to the rotary steerable drillingsystem.

According to an embodiment, the rotary steerable drilling system employsa steering tool constructed to provide better wellbore integrity byusing a steering sleeve as the push component rather than actuator pads.The construction enables application of higher forces as well assteering forces applied closer to the drill bit. The steering sleevealso may be constructed to provide a greater contact area against thesurrounding formation compared to conventional actuator pads. Use of thesteering sleeve reduces or eliminates external moving parts and thusthere are fewer moving parts to fail or to fall free of the system. Theuse of fewer mechanical parts also reduces cost and assembly time whileproviding a more dependable system. The construction minimizes thenumber of threaded fasteners and enables the steering tool to operate ata lower pressure drop. Use of the lower pressure drop reduces thepotential of erosion with respect to the steering tool.

FIG. 1 illustrates an example of a wellsite system in which embodimentsdescribed herein may be employed. The wellsite may be onshore oroffshore. In a wellsite system, a borehole 20 is formed in subsurfaceformations by drilling. The method of drilling to form the borehole 20may include, but is not limited to, rotary and directional drilling. Adrill string 22 is suspended within the borehole 20 and has a bottomhole assembly (BHA) 24 that includes a drill bit 26 at its lower end.

An embodiment of a surface system includes a platform and derrickassembly 28 positioned over the borehole 20. An example of assembly 28includes a rotary table 30, a kelly 32, a hook 34 and a rotary swivel36. The drill string 22 is rotated by the rotary table 30, energized bya suitable system (not shown) which engages the kelly 32 at the upperend of the drill string 22. The drill string 22 is suspended from thehook 34, attached to a traveling block (not shown) through the kelly 32and the rotary swivel 36 which permits rotation of the drill string 22relative to the hook 34. A top drive system can be used in otherembodiments.

An embodiment of the surface system also includes a drilling fluid 38,e.g., mud, stored in a pit 40 formed at the wellsite. A pump 42 deliversthe drilling fluid 38 to the interior of the drill string 22 via one ormore ports in the swivel 36, causing the drilling fluid to flowdownwardly through the drill string 22 as indicated by directional arrow44. The drilling fluid exits the drill string 22 via one or more portsin the drill bit 26, and then circulates upwardly through the annulusregion between the outside of the drill string 22 and the wall of theborehole, as indicated by directional arrows 46. In this manner, thedrilling fluid lubricates the drill bit 26 and carries formationcuttings and particulate matter up to the surface as it is returned tothe pit 40 for recirculation.

The illustrated embodiment of bottom hole assembly 24 includes one ormore logging-while-drilling (LWD) modules 48/50, one or moremeasuring-while-drilling (MWD) modules 52, one or more roto-steerablesystems and motors (not shown), and the drill bit 26. It will also beunderstood that more than one LWD module and/or more than one MWD modulemay be employed in various embodiments, e.g. as represented at 48 and50.

The LWD module 48/50 is housed in a type of drill collar, and includescapabilities for measuring, processing, and storing information, as wellas for communicating with the surface equipment. The LWD module 48/50also may include a pressure measuring device and one or more loggingtools.

The MWD module 52 also is housed in a type of drill collar, and includesone or more devices for measuring characteristics of the drill string 22and drill bit 26. The MWD module 52 also may include one or more devicesfor generating electrical power for the downhole system. In anembodiment, the power generating devices include a mud turbine generator(also known as a “mud motor”) powered by the flow of the drilling fluid.In other embodiments, other power and/or battery systems may be employedto generate power.

The MWD module 52 also may include one or more of the following types ofmeasuring devices: a weight-on-bit measuring device, a torque measuringdevice, a vibration measuring device, a shock measuring device, a stickslip measuring device, a direction measuring device, and an inclinationmeasuring device.

In an operational example, the wellsite system of FIG. 1 is used inconjunction with controlled steering or “directional drilling.”Directional drilling is the intentional deviation of the wellbore fromthe path it would naturally take. In other words, directional drillingis the steering of the drill string 22 so that it travels in a desireddirection. Directional drilling is, for example, useful in offshoredrilling because it enables multiple wells to be drilled from a singleplatform. Directional drilling also enables horizontal drilling througha reservoir. Horizontal drilling enables a longer length of the wellboreto traverse the reservoir, which increases the production rate from thewell.

A directional drilling system also may be used in a vertical drillingoperation. Often the drill bit will veer off of a planned drillingtrajectory because of the unpredictable nature of the formations beingpenetrated or the varying forces that the drill bit experiences. Whensuch a deviation occurs, a directional drilling system may be used toput the drill bit back on course.

A method of directional drilling utilizes a rotary steerable system(“RSS”) to enable drilling along a desired trajectory. In an embodimentthat employs the wellsite system of FIG. 1 for directional drilling, asteerable tool or subsystem 54 is provided. The steerable tool/subsystem54 may be used in an RSS implementation or in other steerable systemsused for drilling a desired borehole, e.g. a wellbore. In an RSS, thedrill string may be rotated from the surface, and downhole devices causethe drill bit to drill in the desired direction. Rotating the drillstring greatly reduces the occurrences of the drill string getting hungup or stuck during drilling. Rotary steerable drilling systems fordrilling deviated boreholes into the earth may be generally classifiedas either “point-the-bit” systems or “push-the-bit” systems.

In an example of a “point-the-bit” rotary steerable system, the axis ofrotation of the drill bit is deviated from the local axis of the bottomhole assembly in the general direction of the new hole. The hole ispropagated in accordance with the customary three-point geometry definedby upper and lower stabilizer touch points and the drill bit. The angleof deviation of the drill bit axis coupled with a finite distancebetween the drill bit and lower stabilizer results in the non-collinearcondition which enables a curve to be generated. This may be achieved ina number of different ways, including a fixed bend at a point in thebottom hole assembly close to the lower stabilizer or a flexure of thedrill bit drive shaft distributed between the upper and lowerstabilizer. In its idealized form, the drill bit does not have to cutsideways because the bit axis is continually rotated in the direction ofthe curved hole. Examples of “point-the-bit” type rotary steerablesystems and their operation are described in U.S. Pat. Nos. 6,394,193;6,364,034; 6,244,361; 6,158,529; 6,092,610; and 5,113,953; and U.S.Patent Application Publication Nos. 2002/0011359 and 2001/0052428.

In an example of a “push-the-bit” rotary steerable system, there is nospecially identified mechanism that deviates the bit axis from the localbottom hole assembly axis. Instead, the requisite non-collinearcondition is achieved by causing either or both of the upper or lowerstabilizers to apply an eccentric force or displacement in a directionthat is orientated with respect to the direction of hole propagation.This may be achieved in a number of different ways, includingnon-rotating (with respect to the hole) eccentric stabilizers(displacement based approaches) and eccentric actuators that apply forceto the drill bit in the desired steering direction. Steering is achievedby creating non co-linearity between the drill bit and at least twoother touch points. In its idealized form, the drill bit cuts sidewaysto generate a curved hole. Examples of “push-the-bit” type rotarysteerable systems and their operation are described in U.S. Pat. Nos.6,089,332; 5,971,085; 5,803,185; 5,778,992; 5,706,905; 5,695,015;5,685,379; 5,673,763; 5,603,385; 5,582,259; 5,553,679; 5,553,678;5,520,255; and 5,265,682.

Referring generally to FIG. 2, an example of steering tool 54 isillustrated as combined with drill bit 26. In this example, the steeringtool 54 may be constructed as a push-the-bit steering tool, however thesteering tool 54 also may be implemented in other types of steeringsystems, e.g. point-the-bit systems. As illustrated in FIG. 2, thisembodiment of the tool 54 comprises a main body 56 coupled with drillbit 26. A steering sleeve 58 is pivotably mounted to the main body 56via a pivot joint 60, such as a gimbal joint 62. A plurality ofactuators 64 is positioned between main body 56 and steering sleeve 58.In various embodiments, actuators 64 are hydraulic actuators which areactuated by fluid, e.g. drilling mud. The hydraulic actuators 64 may beused to provide a high force, low pressure drop, rotary steerable biasunit, operating as a push-the-bit system.

The steering sleeve 58 and the gimbal joint 62 may be oriented such thatthe steering sleeve 58 applies a steering force against a surroundingwall of borehole 20 at an axial position between the gimbal joint 62 andthe drill bit 26. In other words, the pivot joint 60, e.g. gimbal joint62, may be located uphole of the point at which steering force isapplied against the surrounding wall, thus facilitating application ofhigh steering forces and high steerability. When actuators 64 are in theform of hydraulic actuators, the high steering forces can be achievedwith a relatively low pressure drop across the actuators 64.

The actuators 64 are positioned to move radially outward against aninside surface of the steering sleeve 58 so as to cause the steeringsleeve 58 to push against a surrounding wellbore wall. When the steeringsleeve 58 pushes against the surrounding wellbore wall, the drill bit 26is forced in an opposite direction thus steering the drill bit 26 andsteering tool 54. In the embodiment illustrated, the actuators 64 arehydraulic actuators selectively actuated to control the direction ofsteering via hydraulic fluid, e.g. drilling mud, supplied to theactuators 64 under pressure via hydraulic passages 66 formed in mainbody 56. By way of example, the hydraulic actuators 64 may be in theform of ball actuators 68 or other suitable actuators, e.g. hydraulicpiston actuators or electro-mechanical actuators, selectively operableto pivot steering sleeve 58 about pivot joint 60 so as to push againstthe surrounding wellbore wall.

Referring also to FIGS. 3 and 4, an embodiment of gimbal joint 62 isillustrated. In this example, the gimbal joint 62 comprises three bodieseach with one degree of rotational freedom. For example, the threebodies may comprise a portion of the main body 56, a portion of steeringsleeve 58, and a middle ring 68. As illustrated, the portion of mainbody 56 is positioned internally of middle ring 68 and pivotably coupledwith middle ring 68 via pivots 70. The steering sleeve 58 is positionedexternally of middle ring 68 and pivotably coupled with middle ring 68via pivots 72. This arrangement provides the multiple degrees ofrotational freedom and allows an axis of the steering sleeve 58 to bepivoted in a desired direction in three-dimensional space.

Referring generally to FIGS. 5-7, additional views of an embodiment ofthe steering tool 54 and drill bit 26 are illustrated. (It should benoted the cross-sectional illustration of FIG. 5 is taken at anorientation that does not cut through the actuators 64.) In thisexample, the steering sleeve 58 is provided with a sacrificial liner 74and a cuttings guard 76. The sacrificial liner 74 may be disposed alongan interior of the steering sleeve 58 and may be combined with orseparate from the steering sleeve 58. Additionally, the pivots 70, 72may be formed with axis pins 78. In some embodiments, a plurality ofblades 80, e.g. helical blades, may be formed integrally with orattached into steering sleeve 58 and positioned to extend in an outwarddirection toward a surrounding borehole wall.

During a steering operation, the actuators 64 are selectively energizedto push against an inside of the steering sleeve 58, e.g. against aninterior of the sacrificial liner 74 or against other interior surfacesof steering sleeve 58. The steering sleeve 58 is pivoted by theactuators 64 in a desired direction so that the steering sleeve 58pushes against the surrounding wellbore wall. Pushing the sleeve 58against the surrounding wall in a given direction forces the drill bit26 in an opposite direction, thus steering the drill bit 26 and steeringtool 54 along a desired trajectory. In some applications, the steeringsleeve blades 80 may be positioned at an end of the steering sleeve 58closest to drill bit 26 to enable higher dogleg severity.

In some embodiments, the steering force applied can be increased byextending the length of the steering sleeve 58 or by moving the pivotpoint established by pivot joint 60 farther up along the main body 56.The increase in steering force can thus be achieved while utilizing arelatively lower pressure drop (compared to a conventional RSS) toactuate the actuators 64, at least when actuators 64 are in the form ofhydraulic actuators utilizing an actuating fluid, e.g. drilling mud. Thelength of steering sleeve 58 and the position of actuators 64 also maybe selected to obtain a desired, improved mechanical advantage usefulfor a given drilling operation. Such increases in sleeve length and/orother changes also may enable a greater number of actuators 64 to beadded within the steering sleeve 58, thus enabling application of stillgreater force.

Depending on the parameters of a given application, the steering tool 54may utilize a variety of structures and techniques to control theorientation of drill bit 26. For example, various types of joints,actuators, steering sleeves, and other components may be used to enablesteering of the drill bit 26 along a desired trajectory. Similarly, thesize and length of the steering sleeve 58 as well as the number andplacement of actuators 64 may be selected according to the parameters ofa given application. In many applications, the actuators 64 arehydraulic actuators, but electro-mechanical actuators and other suitableactuators may be utilized to provide controlled pivoting of steeringsleeve 58.

Additionally, the steering tool 54 may be employed in a wide variety ofdrilling systems and drilling applications. The unique arrangement oftool body, pivot joint, steering sleeve, and actuators provides adependable, highly steerable tool 54. Because of the relatively lownumber of components and the arrangement of components, the steeringtool 54 also can be constructed at a relatively low cost. Consequently,embodiments described herein may be used to provide a deviated drillingsystem utilizing a high force, low pressure drop, rotary steerable biasunit.

Although a few embodiments of the disclosure have been described indetail above, those of ordinary skill in the art will readily appreciatethat many modifications are possible without materially departing fromthe teachings of this disclosure. Accordingly, such modifications areintended to be included within the scope of this disclosure as definedin the claims. Additionally, it should be understood that references to“one embodiment” or “an embodiment” of the present disclosure are notintended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features. For example, anyelement described in relation to an embodiment herein may be combinablewith any element of any other embodiment described herein. In theclaims, means-plus-function clauses are intended to cover the structuresdescribed herein as performing the recited function and not juststructural equivalents, but also equivalent structures. Thus, although anail and a screw may not be structural equivalents in that a nailemploys a cylindrical surface to secure wooden parts together, whereas ascrew employs a helical surface, in the environment of fastening woodenparts, a nail and a screw may be equivalent structures. It is theexpress intention of the applicant not to invoke means-plus-function forany limitations of any of the claims herein, except for those in whichthe claim expressly uses the words ‘means for’ together with anassociated function.

What is claimed is:
 1. A system for use in a well, comprising: a drillstring comprising a drill bit and a steering tool for controlling thetrajectory of a borehole formed by rotating the drill bit, the steeringtool comprising a main body and a steering sleeve pivotably mounted tothe main body by a joint located to enable pushing contact via thesteering sleeve against a surrounding borehole wall at a locationbetween the joint and the drill bit, the steering sleeve beingselectively pivoted by a plurality of actuators disposed between themain body and the steering sleeve.
 2. The system as recited in claim 1,wherein the plurality of actuators comprises a plurality of hydraulicactuators.
 3. The system as recited in claim 1, wherein the plurality ofactuators comprises a plurality of hydraulic ball actuators.
 4. Thesystem as recited in claim 1, wherein the steering sleeve comprises aplurality of steering blades.
 5. The system as recited in claim 1,wherein the joint comprises a gimbal joint which pivots via pairs ofaxis pins.
 6. The system as recited in claim 1, wherein the steeringsleeve comprises a sacrificial liner.
 7. A method, comprising: pivotablycoupling a steering sleeve, having a sacrificial liner, to a main bodyto form a steering tool; using a sacrificial liner positioned along aninterior of the steering sleeve; locating a plurality of actuatorsbetween the main body and the steering sleeve; coupling the steeringtool to a drill bit; rotating the drill bit; and controlling thedrilling orientation of the drill bit by selectively actuating selectedactuators of the plurality of actuators to cause the steering sleeve topivot against a surrounding borehole wall, thus pushing the drill bit.8. The method as recited in claim 7, wherein pivotably couplingcomprises pivotably coupling the steering sleeve to the main body with agimbal joint.
 9. The method as recited in claim 8, wherein controllingcomprises pivoting the steering sleeve into contact with the surroundingborehole wall at an axial position between the gimbal joint and thedrill bit.
 10. The method as recited in claim 7, wherein locatingcomprises locating a plurality of hydraulic actuators.
 11. The method asrecited in claim 7, wherein locating comprises locating a plurality ofhydraulic ball actuators.
 12. The method as recited in claim 7, furthercomprising constructing the steering sleeve with a plurality of externalblades.
 13. The method as recited in claim 7, further comprising formingthe steering sleeve with a plurality of blades positioned along theexterior of the steering sleeve.
 14. The method as recited in claim 7,further comprising forming the steering sleeve with a plurality ofhelical blades positioned along the exterior.
 15. A system, comprising:a steering tool operable to control a trajectory of a borehole duringdrilling of the borehole, the steering tool comprising: a main body; anda steering sleeve pivotably mounted to the main body by a gimbal jointto enable pushing contact via the steering sleeve against a surroundingborehole wall, the steering sleeve being selectively pivoted by aplurality of actuators disposed between the main body and the steeringsleeve.
 16. The system as recited in claim 15, wherein the steering toolfurther comprises a sacrificial liner positioned along an interior ofthe steering sleeve.
 17. The system as recited in claim 15, wherein thegimbal joint comprises a middle ring having a plurality of pivots, themiddle ring being positioned between the main body and the steeringsleeve.
 18. The system as recited in claim 15, wherein the plurality ofactuators comprises a plurality of hydraulic actuators.
 19. The systemas recited in claim 15, wherein the steering sleeve comprises aplurality of steering blades.
 20. The system as recited in claim 15,further comprising a drill bit coupled to the steering tool, wherein thesteering sleeve is oriented to apply a steering force against asurrounding wall at an axial position between the gimbal joint and thedrill bit.